Nowadays, the Francis turbine is very common usage in the high-head hydroelectric power station. Therefore, optimum design of runner for improving turbine's efficiency is an interesting research topic for research works. In this study, the model of a Francis turbine runner adding splitter blades was designed for considering the optimization of the turbine efficiency. The 2D-flow characteristics around the cascade models are visualized and analysis by mean of CFD code - ANSYS Fluent of RANS and k-E models. The splitter length Ls is changed to make three cases: Ls = 1/3
1/2 and 2/3 the length of the main runner blade. The effects on the turbine power efficiency by changing the length ratio of the splitter are calculated and analysed. From the results of the study, the usage of splitter blade in Francis turbine was clarified by comparison the head loss and reaction force on the blade and cascade.